The circadian system, which strongly influences the occurrence and quality of sleep, is altered with aging. Due to this age-related change in the circadian system, sleep disturbance is common among people over 65. For the past 15 years, the candidate has focused on the elucidation of age- related alternatives of the human circadian system, on the study of the impact of such changes on physiology and behavior, and on the development of approaches to alleviate the negative effects of circadian rhythms changes, particularly with regard to sleep disturbance. The immediate goals of this research are to examine further the efficacy of a treatment for age-related sleep disturbance. The immediate goals of this research are to examine the efficacy of a treatment for age-related sleep disturbance. using time bright light exposure, and to carry out detailed examinations of the processes hypothesized to be crucial to sleep and rhythms regulation. The long-term goals of the candidate's research program are to gain a better understanding of the circadian systems of both normal and pathological aging, to apply circadian principles to the diagnosis and treatment of age-related pathophysiology, to enhance the applicant's scientific expertise in geriatric psychiatry, and to continue a training and education program in human chronobiology. The research proposed will use objective, physiological measures to track long-term response to light treatments in healthy elderly and depressed subjects, and to examine basic characteristic of the aging circadian system in environments without time cues. The research program will be conducted in the Laboratory of Human Chronobiology, widely acknowledge to be one of the world's leading facilities for research related to human sleep and circadian rhythms. The candidate's appointment as Director of the Laboratory, and his promotion to the rank of Associate Professor during the period of this award reflect the Department of Psychiatry's commitment to the candidate's research focus and academic career. The Independent Scientist Award will enable the candidate to further develop and enhance the proposed research program by ensuring a basis of stable, long-term support.